⁦E.⁩ Recovering files from discs and caring for discs

Reading a disc without the program

Why

When you do not have Sigelith Backup, for example on another computer, another system or many years from now. The disc stands on its own: everything you need is on it.

Before you start

  • Open the README.txt file in the main folder of the disc. It is in Polish, English and German and contains the commands for exactly this disc. This manual only summarises them.
  • Windows, macOS and Linux can all read the disc (UDF file system).

Step by step

Reading the files

  • A disc without encryption: the files are in the “data” folder, in the same layout as in the backup. Simply copy them.
  • An encrypted disc (files ending in “.age”): you need the password from the disc card and the age program from the “tools/age” folder on the disc. First you decrypt the disc key (the DISC-KEY.age file) with the password, then the files with the key. The commands are in the README, in point 1. After decrypting, delete the key file: whoever has it can read the disc without the password.
  • You unpack .tar archives (for example LONG-PATHS.tar) with the tar -xf command, built into Windows 10 and newer, macOS and Linux.
  • You join files split into parts (.001, .002…) with the copy /b command on Windows or cat on macOS and Linux. The README gives ready-made commands for every file.

Checking that the files are intact

In the main folder of the disc, run:

  • Linux: sha256sum -c SHA256SUMS
  • macOS: shasum -a 256 -c SHA256SUMS
  • Windows: the PowerShell command from the README, from point 2.

Linux and macOS print “OK” next to every file. Windows lists only files with an error, so no messages means that everything is intact.

Repairing damaged files

  1. Copy the whole disc to a short folder on a drive, for example C:\P. Do not copy a file that cannot be read: the recovery data will rebuild it.
  2. Run the repair with the par2 program from the “tools/par2” folder, using the commands from the README, from point 3.
  3. Check the checksums again.
  4. Record the repaired files on a new disc.

The par2 program does not repair its own files. If after the repair only files from the “par2” folder show an error, your files are intact.

The Sigelith seal

The seal and the file proofs are in the “seal” folder. Sigelith Desktop or the sigelith.org/proof/ page can check them. The README, in the part about the seal, says which file is which.

What you should see

Your files copied from the disc, and when checking: no errors (Windows) or “OK” next to every file (Linux, macOS).

What next

If the disc is starting to fail, record its contents on a new disc while it can still be read.

If something goes wrong

  • Too much damage: the recovery data rebuilds only part of the disc, 15% of the data by default. Read what you can, and recover the remaining files from another backup.
  • Linux does not save a file with a very long name: Linux cannot save a name longer than 255 bytes (an accented letter takes 2 bytes). Unpack such files on Windows.
  • No password for an encrypted disc: see “I don't remember the backup or disc password”.